1. Field of the Invention
The present invention relates to a sound pickup device and a sound pickup method that control a gain of a plurality of microphones.
2. Description of the Related Art
Conventionally, a sound pickup system including a plurality of extension units and a host unit has been proposed (see Japanese Unexamined Patent Application Publication No. 2014-116932, for example). In the sound pickup system of Japanese Unexamined Patent Application Publication No. 2014-116932, each of the extension units is provided with a microphone. The host unit compares the levels of sound signals of sound picked up by the microphone of each of the extension units, and selects an extension unit of the maximum level and outputs. Thus, the sound pickup system of Japanese Unexamined Patent Application Publication No. 2014-116932 outputs sound of a speaker selectively.
In the sound pickup system of Japanese Unexamined Patent Application Publication No. 2014-116932, each of the extension units is provided with an AGC (an automatic gain control amplifier). The AGC decreases a gain in a case in which sound exceeding a predetermined level is input and increases a gain in a case in which sound of less than the predetermined level is input. As a result, the sound pickup system of Japanese Unexamined Patent Application Publication No. 2014-116932 is able to pick up voice of a speaker at some consistent level.
However, the sound pickup system of Japanese Unexamined Patent Application Publication No. 2014-116932 may generate a volume difference when selection of the extension unit is switched since a gain for each microphone may be different. For example, in a state in which a first microphone having a small gain is selected, if an unexpected noise is input to a second microphone having a large gain, the sound pickup system performs processing to switch to the second microphone having a large gain. At this time, since the microphone having a small gain is switched to the microphone having a large gain, volume may become large suddenly.